2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/6521We discuss the expected spectral properties of starbursts of zero and very low metallicity covering their restframe EUV and UV to optical spectra. The main criteria to establish such a "primeval" nature are summarised. Finally we compare these expected properties, including continuum and emission lines, to existing observations of high-z galaxies and briefly discuss future observational prospects.4 pages, To appear in "Multi-wavelength cosmology", Ed. M. Plionis, Kluwer Acad. Press. Related publications and models available at http://webast.ast.obs-mip.fr/sfr/Astrophysicstext